The invention concerns a sensor cassette that can be inserted into an analyzer and comprises a continuous measuring channel for receiving fluidic media and sensory elements for determining chemical and/or physical parameters of the fluidic media.
Measuring systems for determining several parameters in body fluids are important components of clinically relevant analytical methods. The primary aim is in particular a rapid and precise measurement of so-called emergency parameters.
In medicine, point-of-care testing (abbreviated POCT) refers to diagnostic tests which are not carried out in a central laboratory but rather in the hospital directly in the hospital ward, in intensive care units, in anaesthetics and also in outpatient clinics, in dialysis, in the practices of office-based doctors or during transport of a sick person. POCT has the advantage that results are already available after a short period because, on the one hand, there is no need to transport the samples to a specialized laboratory and, on the other hand, no allowances have to be made for the schedules of the laboratory.
Usually so-called emergency parameters are determined such as e.g., the blood gas values (O2, CO2), the pH value, the electrolyte concentrations (Li+, Na+, K+, Mg++, Ca++, Cl−), the concentration of metabolites (glucose, lactate, urea, creatinine), the values for the haemoglobin derivatives (O2Hb, HHb, COHb, MetHb) and bilirubin, the haematocrit value, the determination of values for renal function, blood coagulation values, markers for diseases, cardiac and other measurements. However, it is also possible to carry out urine tests, a blood count or to rapidly detect pathogens with the aid of point-of-care methods.
Many point-of-care tests are designed as test strips. However, if it is intended to determine a plurality of parameters simultaneously or in relation to one another, almost completely automated measuring instruments or analyzers are preferably used which are able to simultaneously determine an entire panel of parameters. The determination of a parameter panel is generally understood as the common determination of several individual parameters as part of a measurement. In this connection parameters are preferably determined together which either can easily be determined together because of common principles of measurement (e.g., haemoglobin derivatives based on one measured spectrum, different electrolytes or metabolites by means of analogous electrochemical or optical detection methods) or which are related to one another for a diagnostic evaluation of the analytical results (e.g., concentrations of different cardiac markers for the differential diagnosis of cardiac diseases or concentrations of different haemoglobin derivatives for a differential diagnosis when disorders of gas metabolism are present).
The measurements generally take place in exchangeable measuring chambers which are equipped with electrochemical (electrodes) and/or optical (optodes) sensory elements. In addition, photometric/spectroscopic methods are also used for this in which the optical properties of the sample to be determined or a color reaction is used for the detection. In this case there are special regions in the sample channel which are for example configured as optical cuvettes (optical measuring windows) which can also be regarded as sensory elements in the sense of this application.
The present invention especially concerns those devices in which the measuring chamber is in the form of a measuring channel in which the medium to be examined such as blood is introduced. As a result the medium to be examined comes into contact with the sensory elements in this measuring chamber in order to enable the actual measuring process. In this connection it is possible to combine several different sensory elements into groups of sensory elements (sensor arrays) which are arranged in a common housing or on a common carrier.
In this connection a measuring chamber block of an analyzer is known from U.S. Pat. No. 5,074,157 A (Marsoner) which can be extended in a modular manner. The field of application of the apparatus can be enlarged by coupling further modules. In order to ensure the leak-proofness of the joints of the individual modules, the coupling parts of the modules have sealing rings. Branch-off channels lead away from the measuring channel linking the individual measuring chambers to coupling parts of the module, to which coupling parts of further measuring chambers may be attached. As a result the measuring path is extended which enables the parameter panel to be extended as required. In order to ensure that prescribed sample temperatures are maintained, it is proposed that the modules be inserted into a receiving block with thermostat control. The individual modules are detachably connected to one another and the measuring chamber block formed by the modules cannot be inserted into the holder of an analyzer in the form of an exchangeable sensor cassette.
U.S. Pat. No. 6,960,466 A (Pamidi et al.) describes a sensor cassette which contains a number of individual measuring electrodes for determining different ‘point-of-care’ parameters such as blood gases, electrolyte values and metabolites which are mounted on a common carrier.
The EP 0846947 (Huber et al.) describes a sensor cassette with electrochemical and/or optical sensors in a planar design which are present on a common sensor component.
A disadvantage of the two known embodiments cited last is that different sensory elements which, for example, require different operating conditions (e.g., different operating temperatures), are present on a single carrier part or sensor component. Another disadvantage is also that the entire sensor cassette with all the sensory elements ends up as a reject if a single sensory element is defective. Another disadvantage is that the known cassettes are not very flexible with regard to a reduction or extension of the parameters panels. New solutions would therefore be desirable for more flexible parameter panels.